{"id":12234,"date":"2025-06-23T10:00:32","date_gmt":"2025-06-23T08:00:32","guid":{"rendered":"https:\/\/sxe-consulting.com\/?p=12234"},"modified":"2025-06-04T09:34:31","modified_gmt":"2025-06-04T07:34:31","slug":"glass-defects-due-to-refractories","status":"publish","type":"post","link":"https:\/\/sxe-consulting.com\/en\/defauts-dans-le-verre-lies-aux-refractaires\/","title":{"rendered":"Glass defects linked to refractories:"},"content":{"rendered":"<p data-start=\"333\" data-end=\"722\">In the<strong data-start=\"340\" data-end=\"362\">Glass industry<\/strong>, the quality of the final product depends on many parameters: glass formulation, melting conditions, furnace atmosphere, but also \u2013 and this is sometimes forgotten \u2013 the quality and durability of the <strong data-start=\"559\" data-end=\"583\">refractory bricks<\/strong>. The choice of refractories and their condition over time have a direct impact on the performance of the furnace and the purity of the glass produced.<\/p>\n<p data-start=\"724\" data-end=\"969\">In this article, we offer an overview of the <strong data-start=\"778\" data-end=\"803\">glass defects<\/strong> most frequently linked to refractories, classifying them by type of refractory material. The aim: to better understand these interactions in order to prevent them more effectively.<\/p>\n<hr data-start=\"971\" data-end=\"974\" \/>\n<h2 data-start=\"976\" data-end=\"1035\">1. AZS refractories: robust but not without risks<\/h2>\n<p data-start=\"1037\" data-end=\"1399\">Refractories of the <strong data-start=\"1054\" data-end=\"1061\">AZS<\/strong> (Alumine &#8211; Zircone &#8211; Silice) sont les plus utilis\u00e9s dans les zones en contact direct avec le bain de verre fondu, notamment dans les fours de fusion. Leur bonne r\u00e9sistance \u00e0 la corrosion et leur faible solubilit\u00e9 les rendent indispensables. Cependant, leur vieillissement ou leur mauvaise mise en \u0153uvre peut engendrer plusieurs d\u00e9fauts :<\/p>\n<h3 data-start=\"1401\" data-end=\"1449\">Refractory inclusions (corundum, zirconia)<\/h3>\n<ul data-start=\"1450\" data-end=\"1791\">\n<li data-start=\"1450\" data-end=\"1525\">\n<p data-start=\"1452\" data-end=\"1525\"><strong data-start=\"1452\" data-end=\"1470\">Defect observed<\/strong> : small opaque white or black spots in the glass.<\/p>\n<\/li>\n<li data-start=\"1526\" data-end=\"1636\">\n<p data-start=\"1528\" data-end=\"1636\"><strong data-start=\"1528\" data-end=\"1539\">Origin<\/strong> : poorly dissolved alumina (corundum) or zirconia crystals resulting from corrosion of the refractory.<\/p>\n<\/li>\n<li data-start=\"1637\" data-end=\"1791\">\n<p data-start=\"1639\" data-end=\"1791\"><strong data-start=\"1639\" data-end=\"1658\">Common cause<\/strong> : progressive dissolution of the core of the <a href=\"https:\/\/sxe-consulting.com\/en\/production-of-electrofused-azs-refractories\/\">AZS bricks<\/a>, especially when the temperature exceeds 1350 \u00b0C, or in the presence of aggressive fluxes.<\/p>\n<\/li>\n<\/ul>\n<h3 data-start=\"1793\" data-end=\"1813\">Striae or cords<\/h3>\n<ul data-start=\"1814\" data-end=\"2018\">\n<li data-start=\"1814\" data-end=\"1900\">\n<p data-start=\"1816\" data-end=\"1900\"><strong data-start=\"1816\" data-end=\"1834\">Defect observed<\/strong> : blurred areas in the glass, visible after tempering or annealing.<\/p>\n<\/li>\n<li data-start=\"1901\" data-end=\"2018\">\n<p data-start=\"1903\" data-end=\"2018\"><strong data-start=\"1903\" data-end=\"1914\">Origin<\/strong> : heterogeneity in the glass-refractory mixture, when the leaching of the material is not uniform.<\/p>\n<\/li>\n<\/ul>\n<h3 data-start=\"2020\" data-end=\"2039\">Bubbles and seeds<\/h3>\n<ul data-start=\"2040\" data-end=\"2224\">\n<li data-start=\"2040\" data-end=\"2104\">\n<p data-start=\"2042\" data-end=\"2104\"><strong data-start=\"2042\" data-end=\"2060\">Defect observed<\/strong> : presence of isolated or clustered bubbles.<\/p>\n<\/li>\n<li data-start=\"2105\" data-end=\"2224\">\n<p data-start=\"2107\" data-end=\"2224\"><strong data-start=\"2107\" data-end=\"2118\">Origin<\/strong> : excessive porosity in the AZS bricks, or secondary reactions with the components of the glass bath.<\/p>\n<\/li>\n<\/ul>\n<h3 data-start=\"2226\" data-end=\"2248\">Good practice:<\/h3>\n<ul data-start=\"2249\" data-end=\"2507\">\n<li data-start=\"2249\" data-end=\"2325\">\n<p data-start=\"2251\" data-end=\"2325\">Choose high-density fused-cast AZS bricks (type AZS 36 or 41).<\/p>\n<\/li>\n<li data-start=\"2326\" data-end=\"2407\">\n<p data-start=\"2328\" data-end=\"2407\">Avoid temperature fluctuations that encourage internal cracking.<\/p>\n<\/li>\n<li data-start=\"2408\" data-end=\"2507\">\n<p data-start=\"2410\" data-end=\"2507\">Set up regular monitoring of wear on sill blocks and side walls.<\/p>\n<\/li>\n<\/ul>\n<hr data-start=\"2509\" data-end=\"2512\" \/>\n<h2 data-start=\"2514\" data-end=\"2586\">2. Silica refractories: thermal fragility and acid corrosion<\/h2>\n<p data-start=\"2588\" data-end=\"2858\">Silica-based refractories are widely used in the upper areas of the furnace (crowns, arches), in particular for their resistance to thermal shock. But their crystalline structure can cause problems in the event of thermal variation or the presence of acids.<\/p>\n<h3 data-start=\"2860\" data-end=\"2879\">Devitrification<\/h3>\n<ul data-start=\"2880\" data-end=\"3068\">\n<li data-start=\"2880\" data-end=\"2963\">\n<p data-start=\"2882\" data-end=\"2963\"><strong data-start=\"2882\" data-end=\"2900\">Defect observed<\/strong> : whitish areas in the glass, fragile or more brittle.<\/p>\n<\/li>\n<li data-start=\"2964\" data-end=\"3068\">\n<p data-start=\"2966\" data-end=\"3068\"><strong data-start=\"2966\" data-end=\"2977\">Origin<\/strong> : release of crystallised free silica, especially in the event of overheating or condensation.<\/p>\n<\/li>\n<\/ul>\n<h3 data-start=\"3070\" data-end=\"3107\">Silica dust or fallout<\/h3>\n<ul data-start=\"3108\" data-end=\"3317\">\n<li data-start=\"3108\" data-end=\"3179\">\n<p data-start=\"3110\" data-end=\"3179\"><strong data-start=\"3110\" data-end=\"3128\">Defect observed<\/strong> : contamination of the bath with fine particles.<\/p>\n<\/li>\n<li data-start=\"3180\" data-end=\"3317\">\n<p data-start=\"3182\" data-end=\"3317\"><strong data-start=\"3182\" data-end=\"3193\">Origin<\/strong> : effritement des vo\u00fbtes ou des joints mal prot\u00e9g\u00e9s, surtout si les temp\u00e9ratures d\u00e9passent les seuils critiques (&gt;1700 \u00b0C).<\/p>\n<\/li>\n<\/ul>\n<h3 data-start=\"3319\" data-end=\"3351\">Risks linked to hydration<\/h3>\n<ul data-start=\"3352\" data-end=\"3475\">\n<li data-start=\"3352\" data-end=\"3475\">\n<p data-start=\"3354\" data-end=\"3475\">Silica is sensitive to moisture, which can weaken the refractory bricks before or during commissioning.<\/p>\n<\/li>\n<\/ul>\n<h3 data-start=\"3477\" data-end=\"3498\">Recommendations:<\/h3>\n<ul data-start=\"3499\" data-end=\"3685\">\n<li data-start=\"3499\" data-end=\"3555\">\n<p data-start=\"3501\" data-end=\"3555\">Store silica bricks away from moisture.<\/p>\n<\/li>\n<li data-start=\"3556\" data-end=\"3626\">\n<p data-start=\"3558\" data-end=\"3626\">Ensure gradual heating when bringing the furnace up to temperature.<\/p>\n<\/li>\n<li data-start=\"3627\" data-end=\"3685\">\n<p data-start=\"3629\" data-end=\"3685\">Plan regular inspections of elevated areas.<\/p>\n<\/li>\n<\/ul>\n<hr data-start=\"3687\" data-end=\"3690\" \/>\n<h2 data-start=\"3692\" data-end=\"3773\">3. Alumina refractories: between mechanical strength and chemical dissolution<\/h2>\n<p data-start=\"3775\" data-end=\"4032\">High-alumina bricks are often used in areas subject to high mechanical stress (wall bases, gantries). Although they resist abrasion well, they are sensitive to certain glass components (particularly alkalis).<\/p>\n<h3 data-start=\"4034\" data-end=\"4054\">Alumina cords<\/h3>\n<ul data-start=\"4055\" data-end=\"4193\">\n<li data-start=\"4055\" data-end=\"4116\">\n<p data-start=\"4057\" data-end=\"4116\"><strong data-start=\"4057\" data-end=\"4075\">Defect observed<\/strong> : pale yellow to brown colouring of the glass.<\/p>\n<\/li>\n<li data-start=\"4117\" data-end=\"4193\">\n<p data-start=\"4119\" data-end=\"4193\"><strong data-start=\"4119\" data-end=\"4130\">Origin<\/strong> : release of alumina or iron oxides through slow corrosion.<\/p>\n<\/li>\n<\/ul>\n<h3 data-start=\"4195\" data-end=\"4222\">Crystalline inclusions<\/h3>\n<ul data-start=\"4223\" data-end=\"4375\">\n<li data-start=\"4223\" data-end=\"4297\">\n<p data-start=\"4225\" data-end=\"4297\"><strong data-start=\"4225\" data-end=\"4243\">Defect observed<\/strong> : microcrystals visible under the microscope or to the naked eye.<\/p>\n<\/li>\n<li data-start=\"4298\" data-end=\"4375\">\n<p data-start=\"4300\" data-end=\"4375\"><strong data-start=\"4300\" data-end=\"4311\">Origin<\/strong> : partial melting of the brick and solidification in the bath.<\/p>\n<\/li>\n<\/ul>\n<h3 data-start=\"4377\" data-end=\"4405\">Usage advice:<\/h3>\n<ul data-start=\"4406\" data-end=\"4642\">\n<li data-start=\"4406\" data-end=\"4456\">\n<p data-start=\"4408\" data-end=\"4456\">Favour dense, low-porosity aluminas.<\/p>\n<\/li>\n<li data-start=\"4457\" data-end=\"4543\">\n<p data-start=\"4459\" data-end=\"4543\">Avoid using them in direct contact with the bath in highly alkaline areas.<\/p>\n<\/li>\n<li data-start=\"4544\" data-end=\"4642\">\n<p data-start=\"4546\" data-end=\"4642\">Reinforce wear areas with combined solutions (AZS + alumina, or mechanical anchoring).<\/p>\n<\/li>\n<\/ul>\n<hr data-start=\"4644\" data-end=\"4647\" \/>\n<h2 data-start=\"4649\" data-end=\"4723\">4. Chromium or spinel refractories: beware of colouring<\/h2>\n<p data-start=\"4725\" data-end=\"4960\">Less common, <a href=\"https:\/\/en.xinguangse.com\/product-center-sintered\/#t2\" target=\"_blank\" rel=\"noopener\">chromium-based refractories<\/a> or magnesia-based refractories are sometimes used in special furnaces (coloured glass, borosilicates, glass fibre). They are robust but present risks of <strong data-start=\"4933\" data-end=\"4959\">unwanted colouration<\/strong>.<\/p>\n<h3 data-start=\"4962\" data-end=\"4994\">Green \/ brown-green colouring<\/h3>\n<ul data-start=\"4995\" data-end=\"5168\">\n<li data-start=\"4995\" data-end=\"5043\">\n<p data-start=\"4997\" data-end=\"5043\"><strong data-start=\"4997\" data-end=\"5015\">Defect observed<\/strong> : greenish tint of the glass.<\/p>\n<\/li>\n<li data-start=\"5044\" data-end=\"5102\">\n<p data-start=\"5046\" data-end=\"5102\"><strong data-start=\"5046\" data-end=\"5057\">Origin<\/strong> : diffusion of chromium oxides into the bath.<\/p>\n<\/li>\n<li data-start=\"5103\" data-end=\"5168\">\n<p data-start=\"5105\" data-end=\"5168\"><strong data-start=\"5105\" data-end=\"5167\">Particularly visible in clear glass (flint glass)<\/strong>.<\/p>\n<\/li>\n<\/ul>\n<h3 data-start=\"5170\" data-end=\"5195\">Preventive measures:<\/h3>\n<ul data-start=\"5196\" data-end=\"5372\">\n<li data-start=\"5196\" data-end=\"5277\">\n<p data-start=\"5198\" data-end=\"5277\">Reserve these materials for areas not exposed to the bath (bottoms, external areas).<\/p>\n<\/li>\n<li data-start=\"5278\" data-end=\"5372\">\n<p data-start=\"5280\" data-end=\"5372\">Monitor oxidising\/reducing atmospheres that can encourage ionic migration.<\/p>\n<\/li>\n<\/ul>\n<hr data-start=\"5374\" data-end=\"5377\" \/>\n<h2 data-start=\"5379\" data-end=\"5463\">Conclusion: refractory bricks to be monitored as critical components<\/h2>\n<p data-start=\"5465\" data-end=\"5855\">Energy efficiency, thermal stability and the quality of the glass produced depend largely on the <strong data-start=\"5578\" data-end=\"5600\">refractory brick<\/strong> used in each zone of the furnace. In the<strong data-start=\"5643\" data-end=\"5665\">Glass industry<\/strong>, preventing defects therefore requires perfect mastery of the physico-chemical properties of refractory materials, but also their proper maintenance and continuous monitoring.<\/p>\n<p data-start=\"5857\" data-end=\"6158\">At <strong data-start=\"5862\" data-end=\"5880\">SXE-Consulting<\/strong>, we support glass manufacturers in the <strong data-start=\"5933\" data-end=\"5959\">selection of refractories <\/strong>and the<strong data-start=\"5963\" data-end=\"5986\">analysis of defects<\/strong>, in order to guarantee optimal production levels while reducing scrap linked to glass quality.<\/p>","protected":false},"excerpt":{"rendered":"<p>Dans l\u2019industrie du verre, la qualit\u00e9 du produit final d\u00e9pend de nombreux param\u00e8tres : formulation du verre, conditions de fusion, atmosph\u00e8re du four, mais aussi \u2013 et on l\u2019oublie parfois \u2013 de la qualit\u00e9 et de la tenue des briques r\u00e9fractaires. Le choix des r\u00e9fractaires et leur \u00e9tat au cours du temps ont un impact [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":12235,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_post_was_ever_published":false},"categories":[91],"tags":[],"class_list":["post-12234","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-refractaires"],"jetpack_featured_media_url":"https:\/\/sxe-consulting.com\/wp-content\/uploads\/2025\/06\/Discoloration.webp","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/sxe-consulting.com\/en\/wp-json\/wp\/v2\/posts\/12234","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/sxe-consulting.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/sxe-consulting.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/sxe-consulting.com\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/sxe-consulting.com\/en\/wp-json\/wp\/v2\/comments?post=12234"}],"version-history":[{"count":0,"href":"https:\/\/sxe-consulting.com\/en\/wp-json\/wp\/v2\/posts\/12234\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/sxe-consulting.com\/en\/wp-json\/wp\/v2\/media\/12235"}],"wp:attachment":[{"href":"https:\/\/sxe-consulting.com\/en\/wp-json\/wp\/v2\/media?parent=12234"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/sxe-consulting.com\/en\/wp-json\/wp\/v2\/categories?post=12234"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/sxe-consulting.com\/en\/wp-json\/wp\/v2\/tags?post=12234"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}